One source of liquid waste compositions which contain copper ions and an organic material which complexes copper is the chemical waste stream or overflow from electroless copper plating baths referred to as copper additive plating. Electroless copper plating baths generally contain cupric ions, a reducing agent, a surfactant, and a complexing agent for cupric ions. In addition, the bath may contain numerous other chemicals, such as, for instance, cyanide ions as disclosed in U.S. Pat. No. 3,844,799 to Underkofler, et al. With respect to electroless copper plating processes, attention is also directed to U.S. Pat. No. 4,152,467 to Alpaugh, et al.
Waste chemical streams from such processes have been processed to remove copper and recover and recycle the complexing agent for the copper in a sequence of steps commonly referred to as "primary recovery". One such "primary recovery" technique includes removing copper from a plating bath overflow composition by plating out copper (i.e., deplating) from solution onto copper cathodes. It is believed that such technique results in the production of undesirable anodic oxidation products of organics present in the composition, such as ethylenedinitrioltetraacetic acid. Such a copper removal process yields a liquid composition with a copper concentration of at least 10-20 ppm as a practical operating lower limit. In addition, in such a process, the iron concentration in solution is increased in view of the reactions occurring at the stainless steel anodes and because of a high concentration of complexing agent in the solution. Besides the copper, the effluent resulting from such a treatment contains a complexing agent for the copper and relatively large amounts of dissolved organic and inorganic salts.
After the copper is removed, the solution is then transferred to another tank where the complexing agent is precipitated by the addition of sulfuric acid to provide a pH of about 2.5 and below. After the complexing agent settles to the bottom of the tank, the solution which is decanted is termed "additive waste".
The complexing agent remaining at the bottom of the tank is washed twice with deionized water and is then recycled to the plating bath. These two wash solutions or decants contain mainly sodium sulfate and formic acid along with dissolved and suspended complexing agent. These wash solutions can be combined with the additive waste solution or held for separate treatment or usage. However, in all cases, significant amounts of suspended complexing agent are transferred into the waste solutions and the particulate complexing agent must be removed by filtration prior to further treatment. As a result, the material is currently unacceptable for direct discharge to existing plant waste treatment systems. Accordingly, as a result, the material is pumped to a storage tank and disposed of by approved methods.
Moreover, even if the additive waste solution contained only sodium sulfate and a few hundred ppm of the complexing agent, it would not be put through the plant waste treatment because the complexing agent would tend to dissolve heavy metals by complexing from the clarifier and piping system and thereby carry these into surrounding natural water sources, such as rivers, where the composition is finally discharged. Although copper would make up the bulk of the complex metal, small amounts of other heavy metals are quite possible.
More recently, Alpaugh, et al. have developed a process, as disclosed in U.S. Pat. No. 4,289,594, whereby the level of the complexing agent is reduced low enough so that the waste composition can be treated subsequently in the usual plant waste treatment systems, including clarifiers, without causing dissolution of heavy metals by complexing from the clarifier and the piping system.
The process disclosed in U.S. Pat. No. 4,289,594 includes contacting the waste solution with an ozone-containing gas in an amount effective to react with and destroy the complexing agent for the copper and irradiating the waste solution with ultraviolet light. Prior to irradiating the solution with ultraviolet light, the concentration of the copper ions in the waste solution is reduced to less than about 8 ppm.
Other suggestions of the use of ozone include U.S. Pat. Nos. 4,332,687 to Daignault, et al. and 3,920,547 to Garrison, et al.
For instance, U.S. Pat. No. 4,332,687 to Daignault, et al. suggests treating a waste solution containing heavy metals complexed with organic compounds by contacting the solution with a mixture of hydrogen peroxide and ozone.
U.S. Pat. No. 3,920,547 to Garrison, et al. suggests a process for destroying cyanides including contacting a cyanide-containing solution with ozone and exposing the solution to ultraviolet radiation.
Also, there have been suggestions such as in U.S. Pat. Nos. 4,012,321 to Koubek and 4,294,703 to Wilms, et al. of using H.sub.2 O.sub.2 in the treatment of waste compositions.
For example, U.S. Pat. Nos. 4,012,321 to Koubek suggests treating an aqueous waste stream containing organic pollutants with H.sub.2 O.sub.2 and irradiating with ultraviolet light.
U.S. Pat. No. 4,294,703 to Wilms, et al. suggests reducing the COD-content of effluent by first adding to the effluent 5-40% of the calculated quantity of H.sub.2 O.sub.2 required for complete oxidation, and then subjecting the effluent to flocculation-absorption. In addition, Wilms, et al. suggest problems in using H.sub.2 O.sub.2 to remove all COD.